During the last two weekends in January, College of Engineering faculty and students were involved in two separate workshops that used exciting, educational, and entertaining projects to inform Girls Scouts about the rudiments of chemistry, electronics, and engineering. Some of the products included the gooiest substance since the Ghostbusters got slimed and jewelry that lights up like fireflies on an August night.

Over the weekend of January 23 and 24, Sarah Perry of the Chemical Engineering Department collaborated with Anne Gershenson of the Department of Biochemistry and Molecular Biology and UMass Amherst Pastry Chef Simon Stevenson in a Girl Scout outreach event in Holyoke. The event attracted 11 girls, ranging from second to fourth grade, from the Girl Scouts of Central and Western Massachusetts. It was billed as “the most OOEY, GOOEY, fantastically SLIMEY program yet.”

What Girl Scout could resist this invitation to the event? “Join UMass Professor Perry, Professor Gershenson, and Chef Simon as they show girls how to make OOBLECK (a mixture of corn starch and water), then experiment with it! What do pizza dough, walking on water, dropping eggs, and OOEY, GOOEY, fantastically SLIMEY oobleck have in common?!”

As Professor Perry said, “Our activities focused around understanding complex fluids. We first discussed the difference between liquids and solids and then discussed examples of materials that are kind of both. I had a splat brain toy[2], which appears to be a sticky solid, but will splat out like a liquid if you throw it hard against the table. The kids really enjoyed playing with the splat ball. We talked about how the difference was the timescale, or how fast you pushed on the ball. Push slow, and it responds like a solid. Splat fast, and it behaves like a liquid.”

Having discussed solids and liquids, the UMass professors then talked about different properties of liquids. As Perry noted, “We performed mixing experiments with food coloring, testing how the dye moved differently in water as opposed to corn starch. Here, we talked about the effects of viscosity.”

Perry added that “One of the coolest experiments that we did involved a Couette viscometer [3](courtesy of William Loinaz, Ashley Carter, and Mishael Coggeshall-Burr from Amherst College). A Couette viscometer[3] is a cylindrical container with an inner cylinder that can rotate. The gap between the two cylinders is filled with corn syrup, and colored liquid is used as a tracer. You then spin the inner cylinder to cause the liquid to flow, mixing the colors.”

The catch is that, because of the viscous nature of the corn syrup and the small size of the gap between the cylinders, if you reverse the flow you can “de mix” the system and recover the colors in their original locations. The girls took turns mixing and un-mixing the colors.

After the mixing experiment, Chef Stevenson led a different, even tastier and more appetizing, experiment, in which the girls tested out how dough (flour + water) made from different types of flour (whole wheat, rye, cake, bread, all purpose, high gluten, pastry) has different properties. After they mixed the dough, the girls then dissolved away all the starch out of their mixtures, leaving behind only the gluten. The chef and the girls then talked about the differences in texture in their samples, and how this difference translates to the types of baked goods for which they are used. Of course, the truth was in the testing, which the Girl Scouts did by enjoying some of the chef’s cookies.

In the final experiment, the girls prepared oobleck from a mixture of corn starch and water. “Oobleck is an interesting material because it is what’s known of as a ‘shear thickening liquid,’” said Perry. “This means that the harder you push on it, the more it resists. So if you tried to scoop up a handful of oobleck it might feel like soft tofu initially, but then once you are holding it, the stuff will relax and ooze out of your hand like a liquid. People have used oobleck for demonstrations where they can ‘run on water.’”

The workshop utilized the oobleck in an egg drop experiment. “We dropped eggs into both a tub of water and a tub of oobleck to test out how they behaved differently,” explained Perry. “Eggs cracked when dropped from only 18 inches into a tub of water. However, we were able to drop eggs from 10 feet (as high as we could reach), and the oobleck cushioned the fall of the egg, preventing it from breaking, due to its shear thickening behavior.”

On the last weekend of January, students from the Society of Women Engineers hosted 11 more Girl Scouts, who spent the morning designing, engineering, and constructing wearable, electronic, programmable, light-up jewelry.

“Our main goal is to attract the girls to engineering by making sure they have a lot of fun learning about it,” explained Dr. Paula Rees, the director of the Diversity Programs Office at UMass Amherst. “The focus of the day is to learn the basics of soldering and programming while making a really cool project to take home to keep or give away as a gift. Most girls made necklaces that they programmed to light up in different colors and patterns. A few girls used the same technology but instead made a pair of earrings.”

All projects utilized two technologies: Adafruit Gemma, a miniature, wearable, Arduino-like, electronics platform board with a lot of might for a low-cost controller; and NeoPixel rings, which consists of 16 LEDs in a ring that can be programmed to make any color by mixing red, green, and blue light (RGB).

This event was especially designed for high school and middle school Girl Scouts and was open to all skill levels. In the process of creating their own computerized jewelry, the Scouts also learned about engineering as a career and got a chance to meet young women working toward their B.S. degrees in a variety of engineering disciplines.

“The purpose is to inspire girls about engineering at an early age,” said Dr. Rees. “We want to create a pipeline of young women into engineering.” (February 2016)